The present invention relates to a data transmission and/or receiving technique and to a data reproducing technique in which a copy inhibit signal is added to main signals such as digital video signals obtained from digital satellite broadcasting signals or digital video signals reproduced from a digital video disc (DVD) or the like.
FIG. 1 illustrates a digital satellite broadcasting system for broadcasting signals, such as video signals which may have been compressed by utilizing a so-called MPEG 2 (moving picture experts group) standard picture compression technique, to a number of subscribers. Such digital satellite broadcasting system generally includes a satellite broadcasting station 210, a broadcasting satellite 220, and a satellite broadcasting receiver 230. The broadcasting satellite 220 may receive broadcast signals transmitted from the broadcasting station 210 and may transmit such received signals to earth. The satellite broadcasting receiver 230, which is mounted in or near the premises of a respective subscriber, may receive the broadcast signals from the broadcasting satellite 220.
More specifically, in the above-mentioned digital satellite broadcasting system, a program may be encoded by an MPEG encoder so as to form an MPEG transport stream (MPEG-TS) which is modulated for satellite broadcasting and transmitted from the satellite broadcasting station 210 by way of a parabola antenna 211 to the broadcasting satellite 220. The broadcasting satellite 220 transmits such program signals so as to be received by the satellite broadcasting receivers 230. As shown in FIG. 1, a respective satellite broadcasting receiver 230 may be coupled to a television receiver 240 and/or a video tape recorder 250.
FIG. 2 illustrates the satellite broadcasting receiver 230. As shown therein, such receiver generally includes a station selection unit 231, a demodulator 232, a data decoder 233, a descrambler 234, an MPEG decoder 235, and a video outputting signal processor 236.
In the satellite broadcasting receiver 230, a channel desired by a user may be selected by use of the station selection unit or tuner 231. A signal of the selected channel or station from the tuner 231 is supplied to the demodulator 232 so as to be demodulated in a predetermined manner. Demodulated digital signals from the demodulator 232 are supplied to the data decoder 233 and the descrambler 234. The data decoder 233 may receive key information from an IC card 237 which may have been provided by the service providers of the respective satellite broadcasting system and may decode such key information and supply the same to the descrambler 234. The descrambler 234 may descramble the demodulated digital signals received from the demodulator 232 by using the key information received from the data decoder 233. Descrambled signals from the descrambler 234 may be supplied to the MPEG decoder 235. If the selected channel signal from the tuner 231 is not scrambled, the descrambler 234 may not perform any descrambling operations and may instead merely supply the output from the demodulator 232 to the MPEG decoder 235. The MPEG decoder 235 may decode the MPEG-TS signals from the descrambler 234 to form decoded digital video signals and may supply the same to the video outputting signal processor 236.
The video outputting signal processor 236 includes a video encoder 361, a macrovision signal generator 362, an adder 363, and a digital-to-analog (D/A) converter 364. The video encoder 361 converts the digital video signals from the MPEG decoder 235 into signals conforming to a predetermined television standard, such as a NTSC standard. Output signals from the NTSC encoder 361 may be combined with output signals from the macrovision signal generator 236 by the adder 363, as hereinafter more fully described. Digital output signals from the adder 363 may be converted to analog video signals in accordance with the predetermined television standard by the D/A converter 364.
The above-mentioned digital satellite broadcasting system may use a so-called pay-per-view service wherein viewers or subscribers are charged a fee to enable viewing of a selected desired program. Typically, in such pay-per-view service, a subscriber may select a desired pay-per-view program from a program table displayed on the television receiver 240 which is supplied thereto from the satellite broadcasting station 210 by way of the broadcasting satellite 220. The subscriber may cause information pertaining to the selected program to be supplied from the satellite broadcasting receiver 230 to the satellite broadcasting station or supervising company by way of a telephone network or the like. The key information utilized for decoding the selected program may be transmitted from the satellite broadcasting station 210 to the respective satellite broadcasting receiver 230 by way of the broadcasting satellite 220, whereupon the desired program is enabled to be viewed and the subscriber is charged.
A pay-per-view program may be displayed on the television receiver 240, but may be inhibited from being recorded by the video tape recorder 250 or the like so as to provide copyright protection. To inhibit such recording, a so-called macrovision or copy protect signal which may inhibit picture recording is added to the pay-per-view program. More specifically, the digital satellite broadcasting station 210 may transmit various additional data, such as key information for decoding, a program table, and/or operating parameters for hardware, along with video and audio data to the satellite broadcasting receiver 230. The received data may be detected or decoded by the data decoder 233 of the satellite broadcasting receiver 230 so as to form a signal for controlling the macrovision signal generator 362. Such control signal may be supplied to the macrovision signal generator 362, whereupon a macrovision signal may be generated and combined with the digital video signals from the NTSC encoder 361 by the adder 363.
The data decoder 233 is illustrated in FIG. 3. As shown therein, the data decoder 233 includes a switch 331, a control code register 332, a control code analyzer 333, and data stream processor 334. Upon detecting a control code packet, the switch 331 is changed so that a control code, which may have 64 bits, is supplied to the control code register 332. The control code from the 64-bit control code register 332 is supplied to the control code analyzer 333 wherein the received control code may be analyzed and parameter setting information and/or on/off control information may be generated and supplied to the macrovision signal generator 362. On the other hand, if signals other than a control code packet are supplied to the switch 331, the switch is changed so that such other signals are supplied to the data stream processor 334 wherein information, such as a program table, may be extracted and processed.
Two types of signals, that is, a pseudo horizontal synchronization pulse and a color stripe, may be utilized as macrovision signals. The two resulting systems will now be described.
In a pseudo horizontal synchronization pulse system, a pseudo horizontal synchronization pulse may be inserted into the vertical blanking period of a video signal, as shown in FIG. 4, so as to cause a malfunction of an automatic gain control (AGC) circuit of the VTR 250 (FIG. 1) and, as a result, cause the picture level to deteriorate to an unacceptable level. As such, acceptable picture recording is inhibited. In a color stripe system, the phase of a number of lines (such as four lines) of a color burst signal may be inverted every 20 lines, as shown in FIG. 5, so as to cause color inversion during reproduction from the VTR 250 and, as a result, cause the picture level to deteriorate to an unacceptable level. As such, acceptable picture recording is inhibited.
The television receiver 240 (FIG. 1) may not include an AGC circuit (as in the VTR 250) so that a displayed picture may not be disturbed or deteriorated by the pseudo horizontal synchronization pulses. However, the television receiver 240 may include an automatic phase control (APC) circuit capable of detecting the phase difference between the color burst signals and an oscillator signal for producing a reference subcarrier wave synchronized with the color burst signal. Nevertheless, the television receiver 240 may not be affected by use of a color stripe system due to a relatively long time constant of the APC circuit.
Thus, if picture signals from the satellite broadcasting receiver 230 are supplied to the video tape recorder (VTR) 250 and the television receiver 240, picture signals having a deteriorated signal quality due to the macrovision signal are recorded on the VTR, while a picture without such picture quality deterioration may be displayed on the television receiver.
Although a particular type or brand of television receiver may not be adversely affected by the use of macrovision signals as described above, other types or brands of television receivers may be adversely affected by such use of macrovision signals. As a result, these latter types of television receivers, which may have parameters different from those of the former type of television receivers, may display video pictures which are deteriorated or subject to interference as, for example, shown in FIG. 6.
Therefore, in the above-described copy protection technique, picture data synthesized or combined with macrovision signals of a pre-set parameter are supplied to all types of television receivers. Although this technique may not adversely affect the performance of some types of television receivers, such technique may adversely affect the performance of other types of television receivers which may have different set parameters, as previously described.
In addition to the above-described technique, a so-called CGMS (copy guard management system) or APS (analog protection system) technique may be utilized for controlling the outputting of a copy protection signal and enabling data pertaining thereto along with picture data or speech data to be recorded by a digital video disc (DVD) or a digital video cassette (DVC) as, for example, shown in FIG. 7. Such CGMS and APS data may be pre-set by the copyright owner. For example, the CGMS data may be 2-bit data, in which `00`, `10`, `01`, and `11` represent copy-free, copying permitted only once, unused, and copying not permitted, respectively. On the other hand, the APS data may be 2-bit data, in which `00`, `01`, `10`, and `11` represent pseudo horizontal synchronization pulse and color stripe signal are both off, pseudo horizontal synchronization pulse is on and color stripe signal is off, pseudo horizontal synchronization pulse is on and two lines of color stripe signal are inserted every 20 lines, and pseudo horizontal synchronization pulse is on and two lines of color stripe signal are inserted every 40 lines, respectively. Through the use of such CGMS and APS data, a particular type of copyright protection signal may (if requested) be formed and utilized. For example, if the CGMS data is set to `11` (copying inhibited), a copy protection signal may be generated and outputted in response to the APS setting value.
Thus, the DVD reproducing device or the DVC reproducing device may synthesize or combine the macrovision signal derived from CGMS and APS data with video data. However, since not all television receivers can operate acceptably with such macrovision or copy protection signals, the picture displayed on such television receivers may be deteriorated or unacceptable. Further, such DVD reproducing device or DVC reproducing device may not readily enable parameters to be altered so as to permit such television receivers to operate acceptably with the macrovision signals.